Orchids (Orchidaceae) are the subject of numerous research studies in the medicament or cosmetics field, aimed at identifying new compounds having advantageous properties. Orchids of the Vanda genus are epiphytic or epilithic orchids of the tropical forest of Asia and of Australia. They are monopodial orchids of low-altitude forests with a high atmospheric humidity. The genus comprises about fifty species with many hybrids. To date, research on plants of the Vanda genus is based on the knowledge and uses of these plants by local populations.
Manandhar et al. (Fitoterapia, 1994, 65 (1), 7-13) have described the use of Vanda cristata in the Kaski district of Nepal, for treating cuts and wounds using a paste based on the plant.
Sigh et al. have studied the traditional phytotherapy with medicinal plants used by the Tharu tribe of the Nainital district in the Uttar Pradesh region in India (Int. J. Pharmacogn., 1994 32 1, 51-58). These authors have described the use of a paste based on Vanda tessallata (synonym: Vanda roxburghii) obtained from the whole plant, and applied with salt to a bone fracture area. The publication also discloses the use of an aqueous extract of this same plant, administered orally for the same purpose.
Compositions intended for skin care, containing an extract of the plant Vanda roxburghii, have been described in Japanese Patent Application JP2006-257056, said extract being used in this composition as an oestrogenic agent for the treatment of skin aging.
Chawla et al. (Ind. J. Pharm. Sci., 1992, 54 (4), 159-61) have described the anti-inflammatory properties of an organic solvent-based extract obtained from Vanda roxburghii roots.
Bulpitt (“The uses and misuses of orchids in medicine”, QJM, 2005, 98 (9), 625-31) indicates that the orchid Vanda coerulea appears to be part of the Indian pharmacopoeia.
Moreover, an extract of the whole plant of Vanda coerulea, sold under the name Biogreen Orchidée Bleue (Biogreen Blue Orchid) by Greentech SA, is also known. This extract is used as an antioxidant in cosmetic compositions.
Aquaporins or water channels are transmembrane protein systems that transport water and small molecules in solution, such as glycerol and urea, for example. The presence of type 3 aquaporins (AQP3) in the human epidermis, more specifically in the plasma membrane of the keratinocytes of human skin, and also the important role that these AQP-3s play in water transport within the human epidermis, are known (SOUGRAT et al., Molecular Biology of the Cell; November 1998; vol. 9, page 499a).
The LEKTI protein (lympho-epithelial Kazal type related inhibitor) is a protease inhibitor and is expressed in the granular layer of the epidermis located under the horny layer. Mutations in the SPINK5 gene, encoding this protein, result in a complete absence of the LEKTI protein in affected individuals, which leads to extreme disturbances of the cutaneous barrier, in particular at the level of the desmosomes.
Desmosomes enable mechanical attachment of the cells to one another, reinforcing the mechanical solidity of the sealing systems, and are binding sites for keratins between two cells (keratinocytes or corneocytes). They thus play an essential role in the cohesion between the cellular compartments which constitute the dermis and the epidermis and in the prevention of intercellular water evaporation, a phenomenon responsible for dryness of the skin.
In the absence of LEKTI production (in the case of patients suffering from Netherton's syndrome), a high degree of fragility of the skin is observed, resulting in severe dehydration.
It has been shown that the horny layer of the skin of knock-out mice (which do not possess the SPINK5 gene) detaches from the rest of the epidermis due to degradation of the desmosomes, which bind the horny layer to the granular layer. This alteration is secondary to the hyperactivity of epidermal proteases which, in the absence of inhibition by LEKTI, degrade one of the key components of desmosomes, Desmoglein 1. LEKTI therefore plays a major role in regulating the process of desquamation of the epidermis by controlling the degradation of these attachment structures.
Stimulating AQP3 and of LEKTI may make it possible both to limit intercellular water evaporation and also to improve water transport within the epidermis. Thus there is a need for a simple, relatively inexpensive cosmetic agent capable of maintaining or reinforcing skin hydration.